Header syntax for QT/BT/TT size

ABSTRACT

There is included a method and apparatus comprising computer code configured to cause a processor or processors to perform obtaining a coding tree unit (CTU) from video data, partitioning the CTU by a quadtree structure, partitioning leaf nodes of the partitioned CTU by at least one of a binary tree structure and a ternary tree structure, and signaling a difference, in base 2 logarithm, between at least one value and a size of a sample resulting from at least one of partitioning the CTU by the quadtree structure and partitioning leaf nodes of the partitioned CTU by the at least one of the binary tree structure and the ternary tree structure.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to provisional application U.S.62/892,246 filed on Aug. 27, 2019 which is hereby expressly incorporatedby reference, in its entirety, into the present application.

BACKGROUND 1. Field

The present disclosure is directed to improving bit-efficiency by a setof advanced video coding technologies including improved QT/BT/TT sizesyntaxes.

2. Description of Related Art

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published theH.265/HEVC (High Efficiency Video Coding) standard in 2013 (version 1)2014 (version 2) 2015 (version 3) and 2016 (version 4). In 2015, thesetwo standard organizations jointly formed the JVET (Joint VideoExploration Team) to explore the potential of developing the next videocoding standard beyond HEVC In October 2017, they issued the Joint Callfor Proposals on Video Compression with Capability beyond HEVC (CfP). ByFeb. 15, 2018, total 22 CfP responses on standard dynamic range (SDR),12 CfP responses on high dynamic range (HDR), and 12 CfP responses on360 video categories were submitted, respectively. In April 2018, allreceived CfP responses were evaluated in the 122 MPEG/10th JVET meeting.As a result of this meeting, JVET formally launched the standardizationprocess of next-generation video coding beyond HEVC. The new standardwas named Versatile Video Coding (VVC), and JVET was renamed as JointVideo Expert Team. The current version of VTM (VVC Test Model), i.e.,VTM 6.

In VVC Draft 6, there are some syntax elements which describe the sizeof QT/BT/TT, as shown in highlighted area in Table 1 and 2 below. Eachof the aforementioned syntaxes specifies the default difference betweenthe base 2 logarithm of two numbers.

TABLE 1 JVET-O2001-vE “Sequence parameter set RBSP syntax”.sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v)sps_log2_diff_min_qt_min_cb_inter_slice ue(v)sps_max_mtt_hierarchy_depth_inter_slice ue(v)sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v) } if(sps_max_mtt_hierarchy_depth_inter_slices != 0 ) {sps_log2_diff_max_bt_min_qt_inter_slice ue(v)sps_log2_diff_max_tt_min_qt_inter_slice ue(v) } if(qtbtt_dual_tree_intra_flag ) {sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if (sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v) } }

TABLE 2 JVET-O2001-vE “General slice header syntax”. if(partition_constraints_override_flag ) {slice_log2_diff_min_qt_min_cb_luma ue(v)slice_max_mtt_hierarchy_depth_luma ue(v) if(slice_max_mtt_hierarchy_depth_luma != 0 )slice_log2_diff_max_bt_min_qt_luma ue(v)slice_log2_diff_max_tt_min_qt_luma ue(v) } if( slice_type = = I &&qtbtt_dual_tree_intra_flag ) { slice_log2_diff_min_qt_min_cb_chromaue(v) slice_max_mtt_hierarchy_depth_chroma ue(v) if(slice_max_mtt_hierarchy_depth_chroma != 0 )slice_log2_diff_max_bt_min_qt_chroma ue(v)slice_log2_diff_max_tt_min_qt_chroma ue(v) } } }

Viewing the above, consider taking syntax sps_log2_diff_min_qt_min_cb_intra_slice_luma as an example specifying thedefault difference between the base 2 logarithm of the minimum size inluma samples of a luma leaf block resulting from quadtree splitting of aCTU and the base 2 logarithm of the minimum coding block size in lumasamples for luma CUs in slices. Thus, it shall be in the range of 0 toCtb Log 2SizeY−MinCb Log 2SizeY, inclusive. Ctb Log 2SizeY is derived aslog 2_ctu_size_minus5+5, so its value is within [5, 6, 7] when CTU sizeis 32×32, 64×64, and 128×128 respectively. Meanwhile, VVC Draft 6specifies that the value of MinCb Log 2SizeY is 2. Thus, the maximumvalue of sps_log 2_diff_min_qt_min_cb_intra_slice_luma is within [3, 4,5] depending on the CTU size.

However, signaling a difference between max QT/BT/TT and min QT/CB isnot bit-efficient, because the max value of QT/BT/TT is typically set toCTU size.

Therefore, there is a desire for a technical solution to such problems.

SUMMARY

To address one or more different technical problems, this disclosuredescribed new syntaxes and use thereof designed to describe QT/TT/BTsize. According to embodiments, these syntaxes change the base from minCB/QT to CTU, and embodiments allow QT/TT/BT size to be signaled usingsmaller numbers. Thus, improved coding efficiency can be achieved.

There is included a method and apparatus comprising memory configured tostore computer program code and a processor or processors configured toaccess the computer program code and operate as instructed by thecomputer program code. The computer program code includes obtaining codeconfigured to cause the at least one processor to obtain a coding treeunit (CTU) from video data, partitioning code configured to cause the atleast one processor to partition the CTU by a quadtree structure,further partitioning code configured to cause the at least one processorto partition leaf nodes of the partitioned CTU by at least one of abinary tree structure and a ternary tree structure, and signaling codeconfigured to cause the at least one processor to signal a difference,in base 2 logarithm, between at least one value and a size of a sampleresulting from at least one of partitioning the CTU by the quadtreestructure and partitioning leaf nodes of the partitioned CTU by the atleast one of the binary tree structure and the ternary tree structure.

According to embodiments, the at least one value comprises a size of theCTU.

According to embodiments, the size of the sample is a base 2 logarithmof a minimum size in luma samples of a luma leaf block resulting frompartitioning the CTU by the quadtree structure.

According to embodiments, the size of the sample is a base 2 logarithmof a maximum size in luma samples of a luma coding block resulting frompartitioning the leaf nodes of the partitioned CTU by the binary treestructure.

According to embodiments, the size of the sample is a base 2 logarithmof a maximum size in luma samples of a luma coding block resulting frompartitioning the leaf nodes of the partitioned CTU by the ternary treestructure.

According to embodiments, the size of the sample is a base 2 logarithmof a maximum size of a chroma coding block resulting from partitioningthe leaf nodes of the partitioned CTU by the binary tree structure.

According to embodiments, the size of the sample is a base 2 logarithmof a maximum size of a chroma coding block resulting from partitioningthe leaf nodes of the partitioned CTU by the ternary tree structure.

According to embodiments, wherein the size of the sample is a base 2logarithm of a minimum size of a chroma leaf block resulting frompartitioning the CTU by the quadtree structure.

According to embodiments, wherein the at least one value comprisesminimum size of a coding block (CB) of the CTU.

According to embodiments, the at least one value is a predeterminedvalue.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a simplified illustration of in accordance with embodiments.

FIG. 2 is a schematic diagram in accordance with embodiments.

FIG. 3 is a schematic diagram in accordance with embodiments.

FIG. 4 is a schematic diagram in accordance with embodiments.

FIG. 5 is a simplified illustration in accordance with embodiments.

FIG. 6 is a simplified illustration in accordance with embodiments.

FIG. 7 is a simplified illustration in accordance with embodiments.

FIG. 8 is a simplified illustration in accordance with embodiments.

FIG. 9A is a simplified illustration in accordance with embodiments.

FIG. 9B is a simplified illustration in accordance with embodiments.

FIG. 10A is a simplified illustration in accordance with embodiments.

FIG. 10B is a simplified illustration in accordance with embodiments.

FIG. 10C is a simplified illustration in accordance with embodiments.

FIG. 11 is a simplified flow illustration in accordance withembodiments.

FIG. 12 is a schematic illustration of a diagram in accordance withembodiments.

DETAILED DESCRIPTION

The proposed features discussed below may be used separately or combinedin any order. Further, the embodiments may be implemented by processingcircuitry (e.g., one or more processors or one or more integratedcircuits). In one example, the one or more processors execute a programthat is stored in a non-transitory computer-readable medium.

FIG. 1 illustrates a simplified block diagram of a communication system100 according to an embodiment of the present disclosure. Thecommunication system 100 may include at least two terminals 102 and 103interconnected via a network 105. For unidirectional transmission ofdata, a first terminal 103 may code video data at a local location fortransmission to the other terminal 102 via the network 105. The secondterminal 102 may receive the coded video data of the other terminal fromthe network 105, decode the coded data and display the recovered videodata. Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 1 illustrates a second pair of terminals 101 and 104 provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal 101 and 104 may code video data captured at a locallocation for transmission to the other terminal via the network 105.Each terminal 101 and 104 also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 1, the terminals 101, 102, 103 and 104 may be illustrated asservers, personal computers and smart phones but the principles of thepresent disclosure are not so limited. Embodiments of the presentdisclosure find application with laptop computers, tablet computers,media players and/or dedicated video conferencing equipment. The network105 represents any number of networks that convey coded video data amongthe terminals 101, 102, 103 and 104, including for example wirelineand/or wireless communication networks. The communication network 105may exchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network 105may be immaterial to the operation of the present disclosure unlessexplained herein below.

FIG. 2 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem 203, that can includea video source 201, for example a digital camera, creating, for example,an uncompressed video sample stream 213. That sample stream 213 may beemphasized as a high data volume when compared to encoded videobitstreams and can be processed by an encoder 202 coupled to the camera201. The encoder 202 can include hardware, software, or a combinationthereof to enable or implement aspects of the disclosed subject matteras described in more detail below. The encoded video bitstream 204,which may be emphasized as a lower data volume when compared to thesample stream, can be stored on a streaming server 205 for future use.One or more streaming clients 212 and 207 can access the streamingserver 205 to retrieve copies 208 and 206 of the encoded video bitstream204. A client 212 can include a video decoder 211 which decodes theincoming copy of the encoded video bitstream 208 and creates an outgoingvideo sample stream 210 that can be rendered on a display 209 or otherrendering device (not depicted). In some streaming systems, the videobitstreams 204, 206 and 208 can be encoded according to certain videocoding/compression standards. Examples of those standards are notedabove and described further herein.

FIG. 3 may be a functional block diagram of a video decoder 300according to an embodiment of the present invention.

A receiver 302 may receive one or more codec video sequences to bedecoded by the decoder 300; in the same or another embodiment, one codedvideo sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel 301, which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver 302 may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver 302 may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory 303 may be coupled inbetween receiver 302 and entropy decoder/parser 304 (“parser”henceforth). When receiver 302 is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer 303 may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer 303 may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder 300 may include a parser 304 to reconstruct symbols313 from the entropy coded video sequence. Categories of those symbolsinclude information used to manage operation of the decoder 300, andpotentially information to control a rendering device such as a display312 that is not an integral part of the decoder but can be coupled toit. The control information for the rendering device(s) may be in theform of Supplementary Enhancement Information (SEI messages) or VideoUsability Information parameter set fragments (not depicted). The parser304 may parse/entropy-decode the coded video sequence received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow principles well known to aperson skilled in the art, including variable length coding, Huffmancoding, arithmetic coding with or without context sensitivity, and soforth. The parser 304 may extract from the coded video sequence, a setof subgroup parameters for at least one of the subgroups of pixels inthe video decoder, based upon at least one parameters corresponding tothe group. Subgroups can include Groups of Pictures (GOPs), pictures,tiles, slices, macroblocks, Coding Units (CUs), blocks, Transform Units(TUs), Prediction Units (PUs) and so forth. The entropy decoder/parsermay also extract from the coded video sequence information such astransform coefficients, quantizer parameter values, motion vectors, andso forth.

The parser 304 may perform entropy decoding/parsing operation on thevideo sequence received from the buffer 303, so to create symbols 313.The parser 304 may receive encoded data, and selectively decodeparticular symbols 313. Further, the parser 304 may determine whetherthe particular symbols 313 are to be provided to a Motion CompensationPrediction unit 306, a scaler/inverse transform unit 305, an IntraPrediction Unit 307, or a loop filter 311.

Reconstruction of the symbols 313 can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser 304. The flow of such subgroup control information between theparser 304 and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder 300 can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit 305. Thescaler/inverse transform unit 305 receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) 313 from the parser 304. It can output blockscomprising sample values, that can be input into aggregator 310.

In some cases, the output samples of the scaler/inverse transform 305can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit 307. In some cases, the intra picture predictionunit 307 generates a block of the same size and shape of the block underreconstruction, using surrounding already reconstructed informationfetched from the current (partly reconstructed) picture 309. Theaggregator 310, in some cases, adds, on a per sample basis, theprediction information the intra prediction unit 307 has generated tothe output sample information as provided by the scaler/inversetransform unit 305.

In other cases, the output samples of the scaler/inverse transform unit305 can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit 306 canaccess reference picture memory 308 to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols 313 pertaining to the block, these samples can be addedby the aggregator 310 to the output of the scaler/inverse transform unit(in this case called the residual samples or residual signal) so togenerate output sample information. The addresses within the referencepicture memory form where the motion compensation unit fetchesprediction samples can be controlled by motion vectors, available to themotion compensation unit in the form of symbols 313 that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory when sub-sample exact motion vectors are in use, motionvector prediction mechanisms, and so forth.

The output samples of the aggregator 310 can be subject to various loopfiltering techniques in the loop filter unit 311. Video compressiontechnologies can include in-loop filter technologies that are controlledby parameters included in the coded video bitstream and made availableto the loop filter unit 311 as symbols 313 from the parser 304, but canalso be responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit 311 can be a sample stream that canbe output to the render device 312 as well as stored in the referencepicture memory 557 for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser 304), the current reference picture 309can become part of the reference picture buffer 308, and a fresh currentpicture memory can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder 300 may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver 302 may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder 300 to properly decode the data and/or to more accuratelyreconstruct the original video data. Additional data can be in the formof, for example, temporal, spatial, or signal-to-noise ratio (SNR)enhancement layers, redundant slices, redundant pictures, forward errorcorrection codes, and so on.

FIG. 4 may be a functional block diagram of a video encoder 400according to an embodiment of the present disclosure.

The encoder 400 may receive video samples from a video source 401 (thatis not part of the encoder) that may capture video image(s) to be codedby the encoder 400.

The video source 401 may provide the source video sequence to be codedby the encoder (303) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source 401 may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source 401 may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more samples depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focuses on samples.

According to an embodiment, the encoder 400 may code and compress thepictures of the source video sequence into a coded video sequence 410 inreal time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController 402. Controller controls other functional units as describedbelow and is functionally coupled to these units. The coupling is notdepicted for clarity. Parameters set by controller can include ratecontrol related parameters (picture skip, quantizer, lambda value ofrate-distortion optimization techniques, . . . ), picture size, group ofpictures (GOP) layout, maximum motion vector search range, and so forth.A person skilled in the art can readily identify other functions ofcontroller 402 as they may pertain to video encoder 400 optimized for acertain system design.

Some video encoders operate in what a person skilled in the art readilyrecognizes as a “coding loop.” As an oversimplified description, acoding loop can consist of the encoding part of an encoder 402 (“sourcecoder” henceforth) (responsible for creating symbols based on an inputpicture to be coded, and a reference picture(s)), and a (local) decoder406 embedded in the encoder 400 that reconstructs the symbols to createthe sample data that a (remote) decoder also would create (as anycompression between symbols and coded video bitstream is lossless in thevideo compression technologies considered in the disclosed subjectmatter). That reconstructed sample stream is input to the referencepicture memory 405. As the decoding of a symbol stream leads tobit-exact results independent of decoder location (local or remote), thereference picture buffer content is also bit exact between local encoderand remote encoder. In other words, the prediction part of an encoder“sees” as reference picture samples exactly the same sample values as adecoder would “see” when using prediction during decoding. Thisfundamental principle of reference picture synchronicity (and resultingdrift, if synchronicity cannot be maintained, for example because ofchannel errors) is well known to a person skilled in the art.

The operation of the “local” decoder 406 can be the same as of a“remote” decoder 300, which has already been described in detail abovein conjunction with FIG. 3. Briefly referring also to FIG. 4, however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder 408 and parser 304 can be lossless, theentropy decoding parts of decoder 300, including channel 301, receiver302, buffer 303, and parser 304 may not be fully implemented in localdecoder 406.

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. The description of encodertechnologies can be abbreviated as they are the inverse of thecomprehensively described decoder technologies. Only in certain areas amore detail description is required and provided below.

As part of its operation, the source coder 403 may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine 407 codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder 406 may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder 403. Operations of the coding engine 407 may advantageouslybe lossy processes. When the coded video data may be decoded at a videodecoder (not shown in FIG. 4), the reconstructed video sequencetypically may be a replica of the source video sequence with someerrors. The local video decoder 406 replicates decoding processes thatmay be performed by the video decoder on reference frames and may causereconstructed reference frames to be stored in the reference picturecache 405. In this manner, the encoder 400 may store copies ofreconstructed reference frames locally that have common content as thereconstructed reference frames that will be obtained by a far-end videodecoder (absent transmission errors).

The predictor 404 may perform prediction searches for the coding engine407. That is, for a new frame to be coded, the predictor 404 may searchthe reference picture memory 405 for sample data (as candidate referencepixel blocks) or certain metadata such as reference picture motionvectors, block shapes, and so on, that may serve as an appropriateprediction reference for the new pictures. The predictor 404 may operateon a sample block-by-pixel block basis to find appropriate predictionreferences. In some cases, as determined by search results obtained bythe predictor 404, an input picture may have prediction references drawnfrom multiple reference pictures stored in the reference picture memory405.

The controller 402 may manage coding operations of the video coder 403,including, for example, setting of parameters and subgroup parametersused for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder 408. The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter 409 may buffer the coded video sequence(s) as created bythe entropy coder 408 to prepare it for transmission via a communicationchannel 411, which may be a hardware/software link to a storage devicewhich would store the encoded video data. The transmitter 409 may mergecoded video data from the video coder 403 with other data to betransmitted, for example, coded audio data and/or ancillary data streams(sources not shown).

The controller 402 may manage operation of the encoder 400. Duringcoding, the controller 405 may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder 400 may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder 400 may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter 409 may transmit additional data withthe encoded video. The source coder 403 may include such data as part ofthe coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

FIG. 5 illustrates intra prediction modes used in HEVC and JEM. Tocapture the arbitrary edge directions presented in natural video, thenumber of directional intra modes is extended from 33, as used in HEVC,to 65. The additional directional modes in JEM on top of HEVC aredepicted as dotted arrows in FIG. 1 (b), and the planar and DC modesremain the same. These denser directional intra prediction modes applyfor all block sizes and for both luma and chroma intra predictions. Asshown in FIG. 5, the directional intra prediction modes as identified bydotted arrows, which is associated with an odd intra prediction modeindex, are called odd intra prediction modes. The directional intraprediction modes as identified by solid arrows, which are associatedwith an even intra prediction mode index, are called even intraprediction modes. In this document, the directional intra predictionmodes, as indicated by solid or dotted arrows in FIG. 5 are alsoreferred as angular modes.

In JEM, a total of 67 intra prediction modes are used for luma intraprediction. To code an intra mode, an most probable mode (MPM) list ofsize 6 is built based on the intra modes of the neighboring blocks. Ifintra mode is not from the MPM list, a flag is signaled to indicatewhether intra mode belongs to the selected modes. In JEM-3.0, there are16 selected modes, which are chosen uniformly as every fourth angularmode. In JVET-D0114 and JVET-G0060, 16 secondary MPMs are derived toreplace the uniformly selected modes.

FIG. 6 illustrates N reference tiers exploited for intra directionalmodes. There is a block unit 611, a segment A 601, a segment B 602, asegment C 603, a segment D 604, a segment E 605, a segment F 606, afirst reference tier 610, a second reference tier 609, a third referencetier 608 and a fourth reference tier 607.

In both HEVC and JEM, as well as some other standards such as H.264/AVC,the reference samples used for predicting the current block arerestricted to a nearest reference line (row or column). In the method ofmultiple reference line intra prediction, the number of candidatereference lines (row or columns) are increased from one (i.e. thenearest) to N for the intra directional modes, where N is an integergreater than or equal to one. FIG. 2 takes 4×4 prediction unit (PU) asan example to show the concept of the multiple line intra directionalprediction method. An intra-directional mode could arbitrarily chooseone of N reference tiers to generate the predictors. In other words, thepredictor p(x,y) is generated from one of the reference samples S1, S2,. . . , and SN. A flag is signaled to indicate which reference tier ischosen for an intra-directional mode. If N is set as 1, the intradirectional prediction method is the same as the traditional method inJEM 2.0. In FIG. 6, the reference lines 610, 609, 608 and 607 arecomposed of six segments 601, 602, 603, 604, 605 and 606 together withthe top-left reference sample. In this document, a reference tier isalso called a reference line. The coordinate of the top-left pixelwithin current block unit is (0,0) and the top left pixel in the 1streference line is (−1,−1).

In JEM, for the luma component, the neighboring samples used for intraprediction sample generations are filtered before the generationprocess. The filtering is controlled by the given intra prediction modeand transform block size. If the intra prediction mode is DC or thetransform block size is equal to 4×4, neighboring samples are notfiltered. If the distance between the given intra prediction mode andvertical mode (or horizontal mode) is larger than predefined threshold,the filtering process is enabled. For neighboring sample filtering, [1,2, 1] filter and bi-linear filters are used.

A position dependent intra prediction combination (PDPC) method is anintra prediction method which invokes a combination of the un-filteredboundary reference samples and HEVC style intra prediction with filteredboundary reference samples. Each prediction sample pred[x][y] located at(x, y) is calculated as follows:pred[x][y]=(wL*R _(−1,y) +wT*R _(x,−1) +wTL*R_(−1,−1)+(64−wL−wT−wTL)*pred[x][y]+32)>>6   (Eq. 2-1)where R_(x,−1), R_(−1,y) represent the unfiltered reference sampleslocated at top and left of current sample (x, y), respectively, andR_(−1,−1) represents the unfiltered reference sample located at thetop-left corner of the current block. The weightings are calculated asbelow,wT=32>>((y<<1)>>shift)  (Eq. 2-2)wL=32>>((x<<1)>>shift)  (Eq. 2-3)wTL=−(wL>>4)−(wT>>4)  (Eq. 2-4)shift=(log 2(width)+log 2(height)+2)>>2  (Eq. 2-5).

FIG. 7 illustrates a diagram 700 in which DC mode PDPC weights (wL, wT,wTL) for (0, 0) and (1, 0) positions inside one 4×4 block. If PDPC isapplied to DC, planar, horizontal, and vertical intra modes, additionalboundary filters are not needed, such as the HEVC DC mode boundaryfilter or horizontal/vertical mode edge filters. FIG. 7 illustrates thedefinition of reference samples Rx,−1, R−1,y and R−1,−1 for PDPC appliedto the top-right diagonal mode. The prediction sample pred(x′, y′) islocated at (x′, y′) within the prediction block. The coordinate x of thereference sample Rx,−1 is given by: x=x′+y′+1, and the coordinate y ofthe reference sample R−1,y is similarly given by: y=x′+y′+1.

FIG. 8 illustrates a Local Illumination Compensation (LIC) diagram 800and is based on a linear model for illumination changes, using a scalingfactor a and an offset b. And it is enabled or disabled adaptively foreach inter-mode coded coding unit (CU).

When LIC applies for a CU, a least square error method is employed toderive the parameters a and b by using the neighboring samples of thecurrent CU and their corresponding reference samples. More specifically,as illustrated in FIG. 8, the subsampled (2:1 subsampling) neighboringsamples of the CU and the corresponding samples (identified by motioninformation of the current CU or sub-CU) in the reference picture areused. The IC parameters are derived and applied for each predictiondirection separately.

When a CU is coded with merge mode, the LIC flag is copied fromneighboring blocks, in a way similar to motion information copy in mergemode; otherwise, an LIC flag is signaled for the CU to indicate whetherLIC applies or not.

FIG. 9A illustrates intra prediction modes 900 used in HEVC. In HEVC,there are total 35 intra prediction modes, among which mode 10 ishorizontal mode, mode 26 is vertical mode, and mode 2, mode 18 and mode34 are diagonal modes. The intra prediction modes are signaled by threemost probable modes (MPMs) and 32 remaining modes.

FIG. 9B illustrates, in embodiments of VVC, there are total 87 intraprediction modes where mode 18 is horizontal mode, mode 50 is verticalmode, and mode 2, mode 34 and mode 66 are diagonal modes. Modes −1˜−10and Modes 67˜76 are called Wide-Angle Intra Prediction (WAIP) modes.

The prediction sample pred(x,y) located at position (x, y) is predictedusing an intra prediction mode (DC, planar, angular) and a linearcombination of reference samples according to the PDPC expression:pred(x,y)=(wL×R−1,y+wT×Rx,−1−wTL×R−1,−1+(64−wL−wT+wTL)×pred(x,y)+32)>>6where Rx,−1, R−1,y represent the reference samples located at the topand left of current sample (x, y), respectively, and R−1,−1 representsthe reference sample located at the top-left corner of the currentblock.

For the DC mode the weights are calculated as follows for a block withdimensions width and height:wT=32>>((y<<1)>>nScale),wL=32>>((x<<1)>>nScale),wTL=(wL>>4)+(wT>>4),with nScale=(log 2(width)−2+log 2(height)−2+2)>>2, where wT denotes theweighting factor for the reference sample located in the above referenceline with the same horizontal coordinate, wL denotes the weightingfactor for the reference sample located in the left reference line withthe same vertical coordinate, and wTL denotes the weighting factor forthe top-left reference sample of the current block, nScale specifies howfast weighting factors decrease along the axis (wL decreasing from leftto right or wT decreasing from top to bottom), namely weighting factordecrement rate, and it is the same along x-axis (from left to right) andy-axis (from top to bottom) in current design. And 32 denotes theinitial weighting factors for the neighboring samples, and the initialweighting factor is also the top (left or top-left) weightings assignedto top-left sample in current CB, and the weighting factors ofneighboring samples in PDPC process should be equal to or less than thisinitial weighting factor.

For planar mode wTL=0, while for horizontal mode wTL=wT and for verticalmode wTL=wL. The PDPC weights can be calculated with adds and shiftsonly. The value of pred(x,y) can be computed in a single step using Eq.1.

Herein the proposed methods may be used separately or combined in anyorder. Further, each of the methods (or embodiments), encoder, anddecoder may be implemented by processing circuitry (e.g., one or moreprocessors or one or more integrated circuits). In one example, the oneor more processors execute a program that is stored in a non-transitorycomputer-readable medium. In the following, the term block may beinterpreted as a prediction block, a coding block, or a coding unit,i.e. CU.

FIG. 10A illustrates an example 1000 of block partitioning by usingQTBT, and FIG. 10B illustrates the corresponding tree representation1001. The solid lines indicate quadtree splitting and dotted linesindicate binary tree splitting. In each splitting (i.e., non-leaf) nodeof the binary tree, one flag is signaled to indicate which splittingtype (i.e., horizontal or vertical) is used, where 0 indicateshorizontal splitting and 1 indicates vertical splitting. For thequadtree splitting, there is no need to indicate the splitting typesince quadtree splitting always splits a block both horizontally andvertically to produce 4 sub-blocks with an equal size.

In HEVC, a CTU is split into CUs by using a quadtree structure denotedas coding tree to adapt to various local characteristics. The decisionon whether to code a picture area using inter-picture (temporal) orintra-picture (spatial) prediction is made at the CU level. Each CU canbe further split into one, two or four PUs according to the PU splittingtype. Inside one PU, the same prediction process is applied and therelevant information is transmitted to the decoder on a PU basis. Afterobtaining the residual block by applying the prediction process based onthe PU splitting type, a CU can be partitioned into transform units(TUs) according to another quadtree structure like the coding tree forthe CU. One of key features of the HEVC structure is that it has themultiple partition conceptions including CU, PU, and TU.

According to embodiments, the QTBT structure removes the concepts ofmultiple partition types, i.e. it removes the separation of the CU, PUand TU concepts, and supports more flexibility for CU partition shapes.In the QTBT block structure, a CU can have either a square orrectangular shape. At the flow diagram 1100 of FIG. 11, according toexemplary embodiments, a coding tree unit (CTU) or CU, obtained at S11,is first partitioned by a quadtree structure at S12. The quadtree leafnodes are further determined whether to be partitioned by a binary treestructure at S14, and if so, at S15, as described with FIG. 10C forexample, there are two splitting types, symmetric horizontal splittingand symmetric vertical splitting, in the binary tree splitting. Thebinary tree leaf nodes are called coding units (CUs), and thatsegmentation is used for prediction and transform processing without anyfurther partitioning. This means that the CU, PU and TU have the sameblock size in the QTBT coding block structure. In VVC, a CU sometimesconsists of coding blocks (CBs) of different color components, e.g. oneCU contains one luma CB and two chroma CBs in the case of P and B slicesof the 4:2:0 chroma format and sometimes consists of a CB of a singlecomponent, e.g., one CU contains only one luma CB or just two chroma CBsin the case of I slices.

According to embodiments, the following parameters are defined for theQTBT partitioning scheme:

-   -   CTU size: the root node size of a quadtree, the same concept as        in HEVC,    -   MinQTSize: the minimum allowed quadtree leaf node size,    -   MaxBTSize: the maximum allowed binary tree root node size,    -   MaxBTDepth: the maximum allowed binary tree depth, and    -   MinBTSize: the minimum allowed binary tree leaf node size.

In one example of the QTBT partitioning structure, the CTU size is setas 128×128 luma samples with two corresponding 64×64 blocks of chromasamples, the MinQTSize, where QT is Quad Tree, is set as 16×16, theMaxBTSize is set as 64×64, the MinBTSize (for both width and height) isset as 4×4, and the MaxBTDepth is set as 4. The quadtree partitioning isapplied to the CTU first to generate quadtree leaf nodes at S12 or S15.The quadtree leaf nodes may have a size from 16×16 (i.e., the MinQTSize)to 128×128 (i.e., the CTU size). If the leaf quadtree node is 128×128,it will not be further split by the binary tree since the size exceedsthe MaxBTSize (i.e., 64×64) as checked at S14. Otherwise, the leafquadtree node could be further partitioned by the binary tree at S15.Therefore, the quadtree leaf node is also the root node for the binarytree and it has the binary tree depth as 0. When the binary tree depthreaches MaxBTDepth (i.e., 4), no further splitting is considered at S14.When the binary tree node has width equal to MinBTSize (i.e., 4), nofurther horizontal splitting is considered at S14. Similarly, when thebinary tree node has height equal to MinBTSize, no further verticalsplitting is considered at S14. Signals at S16 are provided, asdiscussed below with respect to syntaxes which describe QT/TT/BT size,for the procession such as for the leaf nodes of the binary tree thatare further processed by prediction and transform processing, at S17 andsimilarly as discussed herein with respect to such prediction andtransform processing, without any further partitioning. Such signalingmay also be provided at S13 after S12 as shown in FIG. 11 according toexemplary embodiments. In the JEM, the maximum CTU size is 256×256 lumasamples.

In addition according to embodiments, a QTBT scheme supports theability/flexibility for the luma and chroma to have a separate QTBTstructure. Currently, for P and B slices, the luma and chroma codingtree blocks (CTBs) in one CTU share the same QTBT structure. However,for I slices, the luma CTB is partitioned into CUs by a QTBT structure,and the chroma CTBs are partitioned into chroma CUs by another QTBTstructure. This means that a CU in an I slice consists of a coding blockof the luma component or coding blocks of two chroma components, and aCU in a P or B slice consists of coding blocks of all three colorcomponents.

In HEVC, inter prediction for small blocks is restricted to reduce thememory access of motion compensation, such that bi-prediction is notsupported for 4×8 and 8×4 blocks, and inter prediction is not supportedfor 4×4 blocks. In the QTBT as implemented in the JEM-7.0, theserestrictions are removed.

FIG. 10C represents a simplified block diagram 1100 VVC with respect toa Multi-type-tree (MTT) structure 1002 that is included, which is acombination of the illustrated a quadtree (QT) with nested binary trees(BT) and triple-/ternary trees (TT), a QT/BT/TT. A CTU or CU is firstpartitioned recursively by a QT into square shaped blocks. Each QT leafmay then be further partitioned by a BT or TT, where BT and TT splitscan be applied recursively and interleaved but no further QTpartitioning can be applied. In all relevant proposals, the TT splits arectangular block vertically or horizontally into three blocks using a1:2:1 ratio (thus avoiding non-power-of-two widths and heights). Forpartition emulation prevention, additional split constraints aretypically imposed on the MTT, as shown in the simplified diagram 1002 ofFIG. 10C, QT/BT/TT block partitioning in VVC, with respect to blocks1103 (quad), 1104 (binary, JEM), and 1105 (ternary) to avoid duplicatedpartitions (e.g. prohibiting a vertical/horizontal binary split on themiddle partition resulting from a vertical/horizontal ternary split).Further limitations may be set to the maximum depth of the BT and TT.

Herein, new syntaxes are designed to describe QT/TT/BT size according toexemplary embodiments. These syntaxes change the base from min CB/QT toCTU. The proposed method allows QT/TT/BT size to be signaled usingsmaller numbers according to exemplary embodiments, and thus, improvedcoding efficiency, such as bit-efficiency, can be achieved.

According to exemplary embodiments, the syntaxes which describe QT/TT/BTsize, as noted with S16 according to exemplary embodiments, are changed,and it will be understood that in this disclosure, when saying signalingthe delta values between A and B, it may also mean signaling the base 2logarithm of the delta values between A and B. Also, in this disclosure,when saying signaling the absolute value of A, it may also meansignaling the base 2 logarithm of the absolute value of A.

According to exemplary embodiments, signaling may include signaling thedelta values between QT/TT/BT sizes and CTU size.

According to exemplary embodiments, signaling may include explicitlysignaling the absolute values of QT/TT/BT, without delta signaling.

According to exemplary embodiments, signaling may include signaling thedelta values between QT/TT/BT sizes and min CB size.

According to exemplary embodiments, signaling may include signaling thedelta values between QT/TT/BT sizes and min QT size.

According to exemplary embodiments, signaling may include signaling thedelta values between QT/TT/BT sizes and any predefined value.

According to exemplary embodiments, signaling may include signaling thedelta values between QT/TT/BT sizes and any values signaled in anyparameter set (decoding parameter set (DPS), video parameter set (VPS),sequence parameter set (SPS), picture parameter set (PPS) and/oradaptation parameter set (APS)).

According to exemplary embodiments, modified VVC Draft 6 regarding SPSand slice header are shown below with changes highlighted in bold andwith texts with strikethrough indicating deleted texts.

TABLE 3 Sequence parameter set RBSP syntax.

ue(v) sps_log2_diff_ctu_min_qt_intra_slice_luma ue(v)

ue(v) sps_log2_diff_ctu_min_qt_inter_slice ue(v)sps_max_mtt_hierarchy_depth_inter_slice ue(v)sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {

ue(v) sps_log2_diff_ctu_max_bt_intra_slice_luma ue(v)

ue(v) sps_log2_diff_ctu_max_tt_intra_slice_luma ue(v) } if(sps_max_mtt_hierarchy_depth_inter_slices != 0 ) {

ue(v) sps_log2_diff_ctu_max_bt_inter_slice ue(v)

ue(v) sps_log2_diff_ctu_max_tt_inter_slice ue(v) } if(qtbtt_dual_tree_intra_flag ) {sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if (sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {

ue(v) sps_log2_diff_ctu_max_bt_intra_slice_chroma ue(v)

ue(v) sps_log2_diff_ctu_max_tt_intra_slice_chroma ue(v) } }

TABLE 4 General slice header syntax. if(partition_constraints_override_flag ) {

ue(v) slice_log2_diff_ctu_min_qt_luma ue(v)slice_max_mtt_hierarchy_depth_luma ue(v) if(slice_max_mtt_hierarchy_depth_luma != 0 )

ue(v) slice_log2_diff_ctu_max_bt_luma ue(v)

ue(v) slice_log2_diff_ctu_max_tt_luma ue(v) } if( slice_type = = I &&qtbtt_dual_tree_intra_flag ) {

ue(v) slice_log2_diff_ctu_min_qt_chroma ue(v)slice_max_mtt_hierarchy_depth_chroma ue(v) if(slice_max_mtt_hierarchy_depth_chroma != 0 )

ue(v) slice_log2_diff_ctu_max_bt_chroma ue(v)

ue(v) slice_log2_diff_ctu_max_tt_chroma ue(v) } } }

According to exemplary embodiments, sps_log2_diff_ctu_min_qt_intra_slice_luma specifies the default differencebetween the base 2 logarithm of ctu size and the base 2 logarithm of theminimum size in luma samples of a luma leaf block resulting fromquadtree splitting of a CTU (and with or without the base 2 logarithm ofthe minimum coding block size in luma samples for luma CUs in sliceswith slice_type equal to 2 (I)) referring to the SPS. Whenpartition_constraints_override_flag is equal to 1, the defaultdifference can be overridden by slice_log 2_diff_ctu_min_qt_luma presentin the slice header of the slices referring to the SPS. The value ofsps_log 2_diff_ctu_min_qt_intra_slice_luma shall be in the range of 0 toCtb Log 2SizeY−MinCb Log 2SizeY, inclusive. The base 2 logarithm of theminimum size in luma samples of a luma leaf block resulting fromquadtree splitting of a CTU is derived as follows:MinQt Log 2SizeIntraY=log 2_ctu_size_minus5+−sps_log2_diff_ctu_min_qt_intra_slice_luma  Eq. (7-24)

According to exemplary embodiments, sps_log2_diff_ctu_min_qt_inter_slice specifies the default difference betweenthe base 2 logarithm of ctu size and the base 2 logarithm of the minimumsize in luma samples of a luma leaf block resulting from quadtreesplitting and referring to the SPS. Whenpartition_constraints_override_flag is equal to 1, the defaultdifference can be overridden by slice_log 2_diff_ctu_min_qt_luma presentin the slice header of the slices referring to the SPS. The value ofsps_log 2_diff_ctu_min_qt_inter_slice shall be in the range of 0 to CtbLog 2SizeY−MinCb Log 2SizeY, inclusive. The base 2 logarithm of theminimum size in luma samples of a luma leaf block resulting fromquadtree splitting of a CTU is derived as follows:MinQt Log 2SizeInterY=log 2_ctu_size_minus5+5−sps_log2_diff_ctu_min_qt_inter_slice  Eq. (7-25)

According to exemplary embodiments, sps_log2_diff_ctu_max_bt_intra_slice_luma specifies the default differencebetween the base 2 logarithm of ctu size and the base 2 logarithm of themaximum size (width or height) in luma samples of a luma coding blockthat can be split using a binary split (and with or without the minimumsize (width or height) in luma samples of a luma leaf block resultingfrom quadtree splitting of a CTU in slices with slice_type equal to 2(I)) referring to the SPS. When partition_constraints_override_flag isequal to 1, the default difference can be overridden by slice_log2_diff_ctu_max_bt_luma present in the slice header of the slicesreferring to the SPS. The value of sps_log2_diff_ctu_max_bt_intra_slice_luma shall be in the range of 0 to Ctb Log2SizeY−MinQt Log 2SizeIntraY, inclusive. When sps_log2_diff_ctu_max_bt_intra_slice_luma is not present, the value of sps_log2_diff_ctu_max_bt_intra_slice_luma is inferred to be equal to 0.

According to exemplary embodiments, sps_log2_diff_ctu_max_tt_intra_slice_luma specifies the default differencebetween the base 2 logarithm of ctu size and the base 2 logarithm of themaximum size (width or height) in luma samples of a luma coding blockthat can be split using a ternary split (and with or without the minimumsize (width or height) in luma samples of a luma leaf block resultingfrom quadtree splitting of a CTU in slices with slice_type equal to 2(I)) referring to the SPS. When partition_constraints_override_flag isequal to 1, the default difference can be overridden by slice_log2_diff_ctu_max_tt_luma present in the slice header of the slicesreferring to the SPS. The value of sps_log2_diff_ctu_max_tt_intra_slice_luma shall be in the range of 0 to Ctb Log2SizeY−MinQt Log 2SizeIntraY, inclusive. When sps_log2_diff_ctu_max_tt_intra_slice_luma is not present, the value of sps_log2_diff_ctu_max_tt_intra_slice_luma is inferred to be equal to 0.

According to exemplary embodiments, sps_log2_diff_ctu_max_bt_inter_slice specifies the default difference betweenthe base 2 logarithm of ctu size and the base 2 logarithm of the maximumsize (width or height) in luma samples of a luma coding block that canbe split using a binary split (and with or without the minimum size(width or height) in luma samples of a luma leaf block resulting fromquadtree splitting of a CTU in slices with slice_type equal to 0 (B) or1 (P)) referring to the SPS. When partition_constraints_override_flag isequal to 1, the default difference can be overridden by slice_log2_diff_ctu_max_bt_luma present in the slice header of the slicesreferring to the SPS. The value of sps_log 2_diff_ctu_max_bt_inter_sliceshall be in the range of 0 to Ctb Log 2SizeY−MinQt Log 2SizeInterY,inclusive. When sps_log 2_diff_ctu_max_bt_inter_slice is not present,the value of sps_log 2_diff_ctu_max_bt_inter_slice is inferred to beequal to 0.

According to exemplary embodiments, sps_log2_diff_ctu_max_tt_inter_slice specifies the default difference betweenthe base 2 logarithm of ctu size and the base 2 logarithm of the maximumsize (width or height) in luma samples of a luma coding block that canbe split using a ternary split (and the minimum size (width or height)in luma samples of a luma leaf block resulting from quadtree splittingof a CTU in slices with slice_type equal to 0 (B) or 1 (P)) referring tothe SPS. When partition_constraints_override_flag is equal to 1, thedefault difference can be overridden by slice_log 2_diff_ctu_max_tt_lumapresent in the slice header of the slices referring to the SPS. Thevalue of sps_log 2_diff_ctu_max_tt_inter_slice shall be in the range of0 to Ctb Log 2SizeY−MinQt Log 2SizeInterY, inclusive. When sps_log2_diff_ctu_max_tt_inter_slice is not present, the value of sps_log2_diff_ctu_max_tt_inter_slice is inferred to be equal to 0.

According to exemplary embodiments, sps_log2_diff_ctu_max_bt_intra_slice_chroma specifies the default differencebetween the base 2 logarithm of ctu size and the base 2 logarithm of themaximum size (width or height) in luma samples of a chroma coding blockthat can be split using a binary split (and with or without the minimumsize (width or height) in luma samples of a chroma leaf block resultingfrom quadtree splitting of a chroma CTU with treeType equal to DUAL TREECHROMA in slices with slice_type equal to 2 (I)) referring to the SPS.When partition_constraints_override_flag is equal to 1, the defaultdifference can be overridden by slice_log 2_diff_ctu_max_bt_chromapresent in the slice header of the slices referring to the SPS. Thevalue of sps_log 2_diff_ctu_max_bt_intra_slice_chroma shall be in therange of 0 to Ctb Log 2SizeY−MinQt Log 2SizeIntraC, inclusive. Whensps_log 2_diff_ctu_max_bt_intra_slice_chroma is not present, the valueof sps_log 2_diff_ctu_max_bt_intra_slice_chroma is inferred to be equalto 0.

According to exemplary embodiments, sps_log2_diff_ctu_max_tt_intra_slice_chroma specifies the default differencebetween the base 2 logarithm of ctu size and the base 2 logarithm of themaximum size (width or height) in luma samples of a chroma coding blockthat can be split using a ternary split (and with or without the minimumsize (width or height) in luma samples of a chroma leaf block resultingfrom quadtree splitting of a chroma CTU with treeType equal to DUAL TREECHROMA in slices with slice_type equal to 2 (I)) referring to the SPS.When partition_constraints_override_flag is equal to 1, the defaultdifference can be overridden by slice_log 2_diff_ctu_max_tt_chromapresent in the slice header of the slices referring to the SPS. Thevalue of sps_log 2_diff_ctu_max_tt_intra_slice_chroma shall be in therange of 0 to Ctb Log 2SizeY−MinQt Log 2SizeIntraC, inclusive. Whensps_log 2_diff_ctu_max_tt_intra_slice_chroma is not present, the valueof sps_log 2_diff_ctu_max_tt_intra_slice_chroma is inferred to be equalto 0.

According to exemplary embodiments, slice_log 2_diff_ctu_min_qt_lumaspecifies the difference between the base 2 logarithm of ctu size andthe base 2 logarithm of the minimum size in luma samples of a luma leafblock resulting from quadtree splitting of a CTU (and with or withoutthe base 2 logarithm of the minimum coding block size in luma samplesfor luma CUs) in the current slice. The value of slice_log2_diff_ctu_min_qt_luma shall be in the range of 0 to Ctb Log2SizeY−MinCb Log 2SizeY, inclusive. When not present, the value ofslice_log 2_diff_ctu_min_qt_luma is inferred as follows:

-   -   If slice_type equal to 2 (I), the value of slice_log        2_diff_ctu_min_qt_luma is inferred to be equal to sps_log        2_diff_ctu_min_qt_intra_slice_luma    -   Otherwise (slice_type equal to 0 (B) or 1 (P)), the value of        slice_log 2_diff_ctu_min_qt_luma is inferred to be equal to        sps_log 2_diff_ctu_min_qt_inter_slice.

According to exemplary embodiments, slice_log 2_diff_ctu_max_bt_lumaspecifies the difference between the base 2 logarithm of ctu size andthe base 2 logarithm of the maximum size (width or height) in lumasamples of a luma coding block that can be split using a binary splitand the minimum size (width or height) in luma samples of a luma leafblock resulting from quadtree splitting of a CTU in the current slice.The value of slice_log 2_diff_ctu_max_bt_luma shall be in the range of 0to Ctb Log 2SizeY−MinQt Log 2SizeY, inclusive. When not present, thevalue of slice_log 2_diff_ctu_max_bt_luma is inferred as follows:

-   -   If slice_type equal to 2 (I), the value of slice_log        2_diff_ctu_max_bt_luma is inferred to be equal to sps_log        2_diff_ctu_max_bt_intra_slice_luma    -   Otherwise (slice_type equal to 0 (B) or 1 (P)), the value of        slice_log 2_diff_ctu_max_bt_luma is inferred to be equal to        sps_log 2_diff_ctu_max_bt_inter_slice.

According to exemplary embodiments, slice_log 2_diff_ctu_max_tt_lumaspecifies the difference between the base 2 logarithm of ctu size andthe base 2 logarithm of the maximum size (width or height) in lumasamples of a luma coding block that can be split using a ternary split(and with or without the minimum size (width or height) in luma samplesof a luma leaf block resulting from quadtree splitting of a CTU) in thecurrent slice. The value of slice_log 2_diff_ctu_max_tt_luma shall be inthe range of 0 to Ctb Log 2SizeY−MinQt Log 2SizeY, inclusive. When notpresent, the value of slice_log 2_diff_ctu_max_tt_luma is inferred asfollows:

-   -   If slice_type equal to 2 (I), the value of slice_log        2_diff_ctu_max_tt_luma is inferred to be equal to sps_log        2_diff_ctu_max_tt_intra_slice_luma    -   Otherwise (slice_type equal to 0 (B) or 1 (P)), the value of        slice_log 2_diff_ctu_max_tt_luma is inferred to be equal to        sps_log 2_diff_ctu_max_tt_inter_slice.

According to exemplary embodiments, slice_log 2_diff_ctu_min_qt_chromaspecifies the difference between the base 2 logarithm of ctu size andthe base 2 logarithm of the minimum size in luma samples of a chromaleaf block resulting from quadtree splitting of a chroma CTU withtreeType equal to DUAL TREE CHROMA (and with or without the base 2logarithm of the minimum coding block size in luma samples for chromaCUs with treeType equal to DUAL TREE CHROMA) in the current slice. Thevalue of slice_log 2_diff_ctu_min_qt_chroma shall be in the range of 0to Ctb Log 2SizeY−MinCb Log 2SizeY, inclusive. When not present, thevalue of slice_log 2_diff_ctu_min_qt_chroma is inferred to be equal tosps_log 2_diff_ctu_min_qt_intra_slice_chroma.

According to exemplary embodiments, slice_log 2_diff_ctu_max_bt_chromaspecifies the difference between the base 2 logarithm of ctu size andthe base 2 logarithm of the maximum size (width or height) in lumasamples of a chroma coding block that can be split using a binary split(and with or without the minimum size (width or height) in luma samplesof a chroma leaf block resulting from quadtree splitting of a chroma CTUwith treeType equal to DUAL TREE CHROMA) in the current slice. The valueof slice_log 2_diff_ctu_max_bt_chroma shall be in the range of 0 to CtbLog 2SizeY−MinQt Log 2SizeC, inclusive. When not present, the value ofslice_log 2_diff_ctu_max_bt_chroma is inferred to be equal to sps_log2_diff_ctu_max_bt_intra_slice_chroma.

According to exemplary embodiments, slice_log 2_diff_ctu_max_tt_chromaspecifies the difference between the base 2 logarithm of ctu size andthe base 2 logarithm of the maximum size (width or height) in lumasamples of a chroma coding block that can be split using a ternary split(and the minimum size (width or height) in luma samples of a chroma leafblock resulting from quadtree splitting of a chroma CTU with treeTypeequal to DUAL TREE CHROMA) in the current slice. The value of slice_log2_diff_ctu_max_tt_chroma shall be in the range of 0 to Ctb Log2SizeY−MinQt Log 2SizeC, inclusive. When not present, the value ofslice_log 2_diff_ctu_max_tt_chroma is inferred to be equal to sps_log2_diff_ctu_max_tt_intra_slice_chroma.

As described herein, there may be one or more hardware processor andcomputer components, such as buffers, arithmetic logic units, memoryinstructions, configured to determine or store predetermined deltavalues (differences) between ones of the values described hereinaccording to exemplary embodiments.

Accordingly, by exemplary embodiments described herein, the technicalproblems noted above may be advantageously improved upon by one or moreof these technical solutions. That is, according to embodiments, toaddress one or more different technical problems, this disclosuredescribed new syntaxes and use thereof designed to describe QT/TT/BTsize. According to embodiments, these syntaxes change the base from minCB/QT to CTU, and embodiments allow QT/TT/BT size to be signaled usingsmaller numbers. Thus, improved coding efficiency can be achieved.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media or by a specifically configured one or morehardware processors. For example, FIG. 12 shows a computer system 1200suitable for implementing certain embodiments of the disclosed subjectmatter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 12 for computer system 1200 are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 1200.

Computer system 1200 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 1201, mouse 1202, trackpad 1203, touch screen1210, joystick 1205, microphone 1206, scanner 1208, camera 1207.

Computer system 1200 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 1210, or joystick 1205, but there can also be tactilefeedback devices that do not serve as input devices), audio outputdevices (such as: speakers 1209, headphones (not depicted)), visualoutput devices (such as screens 1210 to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system 1200 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW1220 with CD/DVD 1211 or the like media, thumb-drive 1222, removablehard drive or solid state drive 1223, legacy magnetic media such as tapeand floppy disc (not depicted), specialized ROM/ASIC/PLD based devicessuch as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 1200 can also include interface 1299 to one or morecommunication networks 1298. Networks 1298 can for example be wireless,wireline, optical. Networks 1298 can further be local, wide-area,metropolitan, vehicular and industrial, real-time, delay-tolerant, andso on. Examples of networks 1298 include local area networks such asEthernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G,LTE and the like, TV wireline or wireless wide area digital networks toinclude cable TV, satellite TV, and terrestrial broadcast TV, vehicularand industrial to include CANBus, and so forth. Certain networks 1298commonly require external network interface adapters that attached tocertain general-purpose data ports or peripheral buses (1250 and 1251)(such as, for example USB ports of the computer system 1200; others arecommonly integrated into the core of the computer system 1200 byattachment to a system bus as described below (for example Ethernetinterface into a PC computer system or cellular network interface into asmartphone computer system). Using any of these networks 1298, computersystem 1200 can communicate with other entities. Such communication canbe uni-directional, receive only (for example, broadcast TV),uni-directional send-only (for example CANbusto certain CANbus devices),or bi-directional, for example to other computer systems using local orwide area digital networks. Certain protocols and protocol stacks can beused on each of those networks and network interfaces as describedabove.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 1240 of thecomputer system 1200.

The core 1240 can include one or more Central Processing Units (CPU)1241, Graphics Processing Units (GPU) 1242, a graphics adapter 1217,specialized programmable processing units in the form of FieldProgrammable Gate Areas (FPGA) 1243, hardware accelerators for certaintasks 1244, and so forth. These devices, along with Read-only memory(ROM) 1245, Random-access memory 1246, internal mass storage such asinternal non-user accessible hard drives, SSDs, and the like 1247, maybe connected through a system bus 1248. In some computer systems, thesystem bus 1248 can be accessible in the form of one or more physicalplugs to enable extensions by additional CPUs, GPU, and the like. Theperipheral devices can be attached either directly to the core's systembus 1248, or through a peripheral bus 1251. Architectures for aperipheral bus include PCI, USB, and the like.

CPUs 1241, GPUs 1242, FPGAs 1243, and accelerators 1244 can executecertain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM1245 or RAM 1246. Transitional data can be also be stored in RAM 1246,whereas permanent data can be stored for example, in the internal massstorage 1247. Fast storage and retrieval to any of the memory devicescan be enabled through the use of cache memory, that can be closelyassociated with one or more CPU 1241, GPU 1242, mass storage 1247, ROM1245, RAM 1246, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 1200, and specifically the core 1240 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 1240 that are of non-transitorynature, such as core-internal mass storage 1247 or ROM 1245. Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core 1240. A computer-readablemedium can include one or more memory devices or chips, according toparticular needs. The software can cause the core 1240 and specificallythe processors therein (including CPU, GPU, FPGA, and the like) toexecute particular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 1246and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 1244), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method for video coding performed by at leastone processor, the method comprising: obtaining a coding tree unit (CTU)from video data; partitioning the CTU by a quadtree structure;partitioning leaf nodes of the partitioned CTU; signaling a difference,in base 2 logarithm, between a base 2 logarithm of a size of the CTU anda base 2 logarithm of a size of a sample resulting from partitioningleaf nodes of the partitioned CTU; and determining whether to overridesignaling the difference based on a value, in base 2 logarithm, in aslice header of slices reference to a sequence parameter set (SPS). 2.The method for video coding according to claim 1, wherein the size ofthe sample is a base 2 logarithm of a minimum size in luma samples of aluma leaf block resulting from partitioning the CTU by the quadtreestructure.
 3. The method for video coding according to claim 1, whereinthe size of the sample is a base 2 logarithm of a maximum size in lumasamples of a luma coding block resulting from partitioning the leafnodes of the partitioned CTU by a binary tree structure.
 4. The methodfor video coding according to claim 1, wherein the size of the sample isa base 2 logarithm of a maximum size in luma samples of a luma codingblock resulting from partitioning the leaf nodes of the partitioned CTUby a ternary tree structure.
 5. The method for video coding according toclaim 1, wherein the size of the sample is a base 2 logarithm of amaximum size of a chroma coding block resulting from partitioning theleaf nodes of the partitioned CTU by a binary tree structure.
 6. Themethod for video coding according to claim 1, wherein the size of thesample is a base 2 logarithm of a maximum size of a chroma coding blockresulting from partitioning the leaf nodes of the partitioned CTU by aternary tree structure.
 7. The method for video coding according toclaim 1, wherein the size of the sample is a base 2 logarithm of aminimum size of a chroma leaf block resulting from partitioning the CTUby the quadtree structure.
 8. The method for video coding according toclaim 1, wherein the at least one value comprises minimum size of acoding block (CB) of the CTU.
 9. The method for video coding accordingto claim 1, wherein the at least one value is a predetermined value. 10.An apparatus for video coding, the apparatus comprising: at least onememory configured to store computer program code; at least one processorconfigured to access the computer program code and operate as instructedby the computer program code, the computer program code including:obtaining code configured to cause the at least one processor to obtaina coding tree unit (CTU) from video data; partitioning code configuredto cause the at least one processor to partition the CTU by a quadtreestructure; further partitioning code configured to cause the at leastone processor to partition leaf nodes of the partitioned CTU; signalingcode configured to cause the at least one processor to signal adifference, in base 2 logarithm, between a base 2 logarithm of a size ofthe CTU and a base 2 logarithm of a size of a sample resulting frompartitioning leaf nodes of the partitioned CTU; and determining codeconfigured to cause the at least one processor to determine whether tooverride signaling the difference based on a value, in base 2 logarithm,in a slice header of slices reference to a sequence parameter set (SPS).11. The apparatus for video coding according to claim 10, wherein thesize of the sample is a base 2 logarithm of a minimum size in lumasamples of a luma leaf block resulting from partitioning the CTU by thequadtree structure.
 12. The apparatus for video coding according toclaim 10, wherein the size of the sample is a base 2 logarithm of amaximum size in luma samples of a luma coding block resulting frompartitioning the leaf nodes of the partitioned CTU by a binary treestructure.
 13. The apparatus for video coding according to claim 11,wherein the size of the sample is a base 2 logarithm of a maximum sizein luma samples of a luma coding block resulting from partitioning theleaf nodes of the partitioned CTU by a ternary tree structure.
 14. Theapparatus for video coding according to claim claim 10, wherein the sizeof the sample is a base 2 logarithm of a maximum size of a chroma codingblock resulting from partitioning the leaf nodes of the partitioned CTUby a binary tree structure.
 15. The apparatus for video coding accordingto claim claim 10, wherein the size of the sample is a base 2 logarithmof a maximum size of a chroma coding block resulting from partitioningthe leaf nodes of the partitioned CTU by a ternary tree structure. 16.The apparatus for video coding according to claim claim 10, wherein thesize of the sample is a base 2 logarithm of a minimum size of a chromaleaf block resulting from partitioning the CTU by the quadtreestructure.
 17. The apparatus for video coding according to claim 10,wherein the at least one value comprises minimum size of a coding block(CB) of the CTU.
 18. A non-transitory computer readable medium storing aprogram configured to cause a computer to: obtain a coding tree unit(CTU) from video data; partition the CTU by a quadtree structure;partition leaf nodes of the partitioned CTU; signal a difference, inbase 2 logarithm, between a base 2 logarithm of a size of the CTU and abase 2 logarithm of a size of a sample resulting from partitioning leafnodes of the partitioned CTU; and determining whether to overridesignaling the difference based on a value, in base 2 logarithm, in aslice header of slices reference to a sequence parameter set (SPS).